Korean Journal of Neuromuscular Disorders Vol. 4, 2012 ISSN 2092-5077 Korean Journal of Neuromuscular Disorders Vol. 4, June 2012 팔다리이음근육디스트로피의진단및치료 연세대학교의과대학신경과학교실 박형준정주리최영철 Diagnosis and Therapy of Limb Girdle Muscular Dystrophy Hyung Jun Park, MD, Julie Jeong, MD, Young-Chul Choi, MD, PhD Department of Neurology, Brain Korea 21 Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea KEYWORDS Limb girdle muscular dystrophy, Diagnosis, Treatment The limb girdle muscular dystrophy (LGMD) is an inherited myopathy with characteristic feature of muscular weakness predominantly affecting shoulder and pelvic girdles. Since the 1990s its classification has been completely revised because of the progress of molecular diagnosis and protein analysis. To diagnose a particular subtype of LGMD may be difficult and requires a comprehensive appraoch due to wide clinical and genetic heterogeneity. To reach a precise diagnose, the following steps generally are needed. The first step is to analyse the clinical presentation and serum creatine kinase level. The second step is a protein analysis such as immunohistochemistry and Western blotting in the muscle biopsy. The third step is a mutational analysis of defective protein to confirm the final diagnosis. However, advances in molecular technologies make mutational analysis the golden standard of LGMD diagnosis. Current treatment of LGMD remains palliative and supportive. However, the uderstanding of novel pathogenic mechanisms wll suggest therpeutic approaches and future clinical trials. This articel summarizes current diagnostic and therapeutic approcahes of LGMD. 서론 팔다리이음근육디스트로피 (limb girdle muscular dystrophy, LGMD) 는 1954년 Walton 과 Natrass 에의해처음정의되었다. 당시 LGMD 는임상적으로진단이용이한듀센형근육디스트로피 (Duchenne muscular dystrophy), 베커형근육디스트로피 (Becker muscular dystrophy) 와얼굴어깨상완근육디스트로피 (facioscapulohumoral muscular dystrophy) 를제외한근위부의근력약화를갖는유전성근육병들로정의되었다. 1 그러나 1990년대의연관분석 (Linkage analysis) 과디스트로핀연관단백의연구로 LGMD 가 dystrophin 연관복합체, 세포막의단백, 효소등다양한원인단백의손상으로인한유전성근육병의집합임이밝혀졌다. 분자유전학기술의발달에따라현재는 23개 LGMD 의아형이밝혀져있다. LGMD 은상염색체우성유전인 1형 (LGMD1) 과상염색체열성유전인 2형 (LGMD2) 으로 1차분류하고, 원인유전자또는유전자가밝혀진순서에따라서알파벳으로접미사를붙여서명명한다. 그러나아직까지 LGMD 의진단을위해서는침습적인검사인근육생검이나높은비용의유전자검사가필요하기때문에많은환자들이정 Received: May 31, 2012 / Accepted: June 10, 2012 Address for correspondence: Young-Chul Choi, MD Department of Neurology, Gangnam Severance Hospital, Yonsei University College of Medicine, 211 Eonju-ro, Gangnam-gu, Seoul 135-720, Korea Tel: +82-2-2019-3323,3320, Fax: +82-2-3462-5904, E-mail: ycchoi@yuhs.ac 16 대한신경근육질환학회지 2012
HJ Park, et al. Diagnosis and Therapy of Limb Girdle Muscular Dystrophy 확한진단을받지못하고있다. 본논문에서는 LGMD 의진단을위한접근방법및치료와대표적인아형의특징을정리하고, 2명의증례에대해서살펴보기로하겠다. 본론 1. 진단적접근방법 현재까지 LGMD1 형에속하는 8개의아형과 LGMD2 형에속하는 15개의아형이알려져있다. 2 LGMD 의진단을 위한일차적접근은가족력, 근육의침범양상과날개견갑골및관절구축과같은특징적인병력과임상양상을확인하는것이다. 이때혈중크레아틴키나아제 (creatine kinase, CK) 의수치와심장및폐기능검사도진단을위한중요한근거가된다. 이런과정을통해서 Duchenne 근육디스트로피, FSHD 척수근육위축증등의질환들을감별진단하고, LGMD 의아형을국소화할수있다. Table 1은대표적인 LGMD 아형의원인유전자및임상적특징을정리한것이다. 비록각아형에따라임상양상이다양하고, 같은아형혹은같은유전형에서도표현형이다르기때문에임상적 Table 1. Clinicial characteristics of the limb girdle muscular dystrophies LGMD form Locus Protein Typical onset a Progress Cardiomyopathy a Key features from history Autosomoal dominant LGMD1A 5q31 Myotilin Adult Slow Not observed Dysarthria (or nasal voice) Distal weakness Contracture of Achilles tendon LGMD1B 1q11-q21 Lamin A/C Any age Slow Often observed Contracture Cadiac disease LGMD1C 3p25 Caveolin 3 Any age Slow/ moderate Autosomal recessive LGMD2A 15q15.1 Calpain-3 1st-2nd decade (2-40years) LGMD2B 2p13 Dysferlin 2nd-3rd decade (10-73 years) LGMD2C 13q12 γ-sarcoglycan 1st-2nd decade LGMD2D 17q21 α-sarcoglycan (3-20 years) LGMD2E 4q12 β-sarcoglycan LGMD2F 5q33 δ-sarcoglycan Moderate/ rapid CK level b Prevalence 3-4X Common mutation in all populations 1-6X Present worldwide Frequent Rippling muscle disease 10X Present worldwide at low frequency Rarely observed Winged scapula Contracture of Achilles tendon 3-20X The Most common forms worldwide Slow Possible Difficulty standing on tiptoe 5-40X Present worldwide Rapid Often severe, rare in 2D Clinically may resemble DMD/BMD Winged scapula Hypertrophy of calves 10-70X Present worldwide LGMD2G 17q12 Telethonin 2nd decade Slow Yes Distal weakness and wasting may be present 10X Rarely in Brazil LGMD2H 9q31-q34 TRIM32 2nd decade Slow Not observed Possible mild facial weakness 5-15X Hutterite populations of Canadian LGMD2I 19q13.3 FKRP 1st-2nd decade (3-20 years) Moderate Yes Clinically may resemble DMD/BMD LGMD2J 2q31 Titin 1st decade Severe Not observed History of distal weakness in heterozygotes LGMD2K 9q34 POMT1 Birth-6 years Slow Not observed Upper lim weakness may be worse than lower weakness 10-20X Northern European 10-40X Only in Finland 10-40X Few cases LGMD2L 11p13-p12 ANO5 3rd decade Slow Not observed 1-15X In Nothern Europe LGMD2M 9q31 Fukutin <1 yeat Moderate Sometimes Calf hypertrophy 10-70X Japan LGMD2N 14q24 POMT2 Early child Slow Rare 5-15X Few cases a Also indicates mild signs of cardiac involvement. b Indicates the range of serum creatine kinase (CK) levels that is observed in about 80% of patients. Abbreviation: DMD/BMD, Duchenne/Becker muscular dystrophy. Korean Journal of Neuromuscular Disorders 2012 17
Korean Journal of Neuromuscular Disorders Vol. 4, 2012 특징만으로진단할수는없지만가능성높은아형을선별할수있는중요한과정이다. 임상적특징의확인후에는단백의결손과유전자의이상을확인하는작업이필요하다. 일반적으로단백결손의확인을위해근육조직의면역조직화학염색 (Immunohistochemistry) 이나웨스턴블럿 (Western blotting) 을사용한다. 단백의결손을확인한후에는해당단백을합성하는유전자의돌연변이를확인하는작업을거치게된다. 이러한일렬의절차를통해서, LGMD 환자의 75% 를진단할수있었다는보고가있다. 3 2. 원인단백분석 원인단백분석을위해서는침습적인근육조직검사가필요하다. 근육조직의통상적인염색으로신경성질환, 대사성근병증 ( 폼페병등 ), 염증성근육병등을감별할수있다. 분엽섬유 (lobulated fiber), 공포가있는섬유 (vacuolated fiber), ragged red fiber를찾는다면몇몇근육병들로국한시키는것에는도움이될수있다. 그러나진단을위한원인단백의결손의확인에는근육조직에대한면역조직화학염 색이나웨스턴블럿이필요하다. 면역조직화학염색은조직내의단백분포를보여주고, 시간소요가적으며, 경제적인반면, 웨스턴블럿은단백의분자량의측정및단백의양을정량화가가능하다. 그러나원인단백을분석할때는 dystrophin의결손으로인해서 sarcoglycan 및 α-dystroglycan 의결손이생기는것처럼이차적인단백결손에대한고려가필요하다. 따라서많은단백을동시에검사하는것이필요하다. 이러한이유로통상적인연구에는비용과노력이적게드는면역조직화학염색이선호된다. 그러나정량화가필요하거나 LGMD2A의원인단백인 calpain 3과같은효소단백의소실을확인하기위해서는웨스턴블럿이필요하다. 3. 유전자검사유전자검사는근육조직검사보다덜침습적이고원인유전자의염기서열변화를실제로확인할수있기때문에선호된다. 그러나 LGMD 의원인유전자들은그수가많고, titin (TTN) 유전자처럼 312 exon 을갖는경우도있어서모든유전자를확인하는작업은너무나많은돈과노력이소 A B C D Figure 1. Illustration of different capture methods. Light blue represent desired sequence (exon), red bars represent unwanted sequence (intron). (A) Solid-phase hybridization. Bait probes (light blue and black) complementary to the desired sequence are synthesized on a microarray. Fragmented genomic DNA is applied, and the desired fragments hybridize. The array is washed, and desired fragments are eluted. (B) Liquid-phase hybridization. Bait probes (light blue and black) complementary to the desired regions(exons) are synthesized, often using microarray technology. The probes are generally biotinylated (asterisk). The bait probes are mixed with fragmented genomic DNA, and the desired fragments hybridize to baits in solution. Streptavidin beads (black circles) are added to allow physical seperation. The bead-bait complexes are washed, and desired DNA is eluted. (C) Molecular Inversion Probes (MIP). Single-stranded probes composed of a univeral linker backbone (black line) and arms complementary to the sequence flanking desired regions (red and white) are synthesized, often using microarray or microfluidics technology. The probes are added to genomic DNA and hybridize in an inverted manner. A polymerase (yellow oval) fills in the gap between the two arms. A ligase (yellow star) seals the nick, resulting in a closed single-strand circle. Genomic DNA is digested with exonucleases, and the capture DNA is amplified using sequences in the universal backbone. (D) Primer Extension Capture (PEC) Biotinylated primers (red and white) are added to fragmented genomic DNA, where they hybridze to the deisred sequence. A polymerase (yellow oval) extends the primer, creating a tighter interaction. Streptavidin beads (black circles) are added and are used to physically seperate the desired DNA from the unwanted DNA. The desired DNA is then eluted. (Modified from Teer et al.) 8 18 대한신경근육질환학회지 2012
HJ Park, et al. Diagnosis and Therapy of Limb Girdle Muscular Dystrophy 요된다. 따라서, 현재의유전자검사는조직검사로단백결손을확인한후해당유전자에대한돌연변이를찾는방식으로이루어진다. 그러나이탈리아연구진처럼 181명 LGMD 환자를대상으로 8개의흔한유전자 (calpain-3, dysferlin, γ-sarcoglycan, α-sarcoglycan, β-sarcoglycan, δ-sarcoglycan, Fukutin-related protein, caveolin-3) 를검사해서 72.9% 의환자를진단한사례도있다. 4 유전자진단의걸림돌인비용과노력을줄이기위해서 Homozygosity Mapping, Single Strand Confirmation Polymorphism analysis (SSCP), Denaturing High Pressure Liquid Chromatography (DHPLC) 등의여러방법들이시도되고있다. 5-7 messenger RNA (mrna) 의염기서열분석도하나의방법이될수있으나 calpain-3과 dysferlin을제외하면근육조직검사가필요하다는한계점이있다. 여러방법중에서도 2007년부터시작된차세대염기서열분석방법 (next generation sequencing, NGS) 의도입은여러검체를동시에분석할경우비용과노력을획기적으로절감시켰다. 특히사람의전체유전체 (genome) 의 2% 만을구성하지만아미노산의배열을결정하는 exon만을분석하는 exome sequencing 방법은유전자진단의접근성을더욱더높여주었다. 8 Exome sequencing을위해서는 Fig. 1과같은방법으로원하는부분의염기서열을 capture한후 NGS sequencer로염기서열을해독하는과정을거치게된다. NGS sequencer의해독방법은제조회사와개발된시점에따라서다양하다. 비록현재까지의 NGS 분석은다량의검체를대상으로할때만비용절감이가능하고, 긴염기서열을한번에해독할수없지만, 분자유전학의빠른발달은단점을빠르게보완하고비용을더욱줄어들고있다. 머지않은장래에 LGMD 의진단도듀센형근육디스트로피나얼굴어깨상완근육디스트로피와마찬가지로유전자검사가침습적인근육조직검사보다선행하게될것이다. 는근본적인치료제가아닐뿐만아니라체중증가, 골다공증, 성장지연등의많은합병증을초래할수있다. 손상된유전자의근본적인치료방법으로분자치료가활발하게연구되고있다. LGMD2B 의동물모델에대해 exon skipping 방법, 동맥으로 mesangioblast 를주입하는세포치료, AAV 매개의유전자치료등이여기에속하지만아직은동물실험단계에머물러있다. 임상시험으로는 LGMD2D 환자의짧은발가락폄근 (extensor digitorum brevis) 에 adeno-assoicated virus (AAV) 를매개한유전자치료를시행하였더니 6개월후에도 α-sarcoglycan 유전자의발현이확인되었다는보고가있을뿐이다. 15,16 그러나듀센형근육디스트로피의치료에서 exon skipping 방법이고무적인결과를보이는만큼가까운미래에는 LGMD 에서도임상연구가진행될것으로생각된다. 5. 각아형별특징 1) LGMD1A (myotillinopathy) LGMD1 은 2형에비해서드물어서전체 LGMD 의 10% 이하이다. LGMD1A 는 myotilin 유전자이상으로발현된다. 17,18 일반적으로 18세에서 35세의성인에서발현되어근위부와원위부의근력약화가동시에나타나고, myotilin 유전자의돌연변이가 LGMD 가아닌원위부근육병으로발현되는경우도많다. 구어장애와아킬레스건의구축도종종동반된다. 이외에도심혈관계, 호흡기계, 백내장등의합병증이있던가계도있어서이에대한주의가필요하다. 혈중 CK는정상이거나 5배정도소폭상승한다. 근육조직검사상공포와 desmin 과 myotilin같은근원섬유단백 (myofibrillar protein) 의축적을관찰할수있다. 그러나이러한조직학적변화는 myotilin 뿐만아니라 desmin, ZASP, αβ-crystallin, filamin C 의손상으로인한 myofibrillar myopathy의공통적인소견이다. 4. 치료현재까지의 LGMD 치료는보조적인대증치료에국한되어있다. 수면중의장하지보조기 (knee-ankle-foot orthoses) 착용과물리치료는관절의구축을막아보행가능기간을늘려준다. 근육디스트로피의약물치료제중스테로이드는듀센형근육디스트로피에서유일하게효과를입증한약제이다. 9-11 LGMD 2D, 2I, 2M의환자에에서스테로이드의효과에대한증례및소규모연구가있으나, 12-14 대규모연구결과는없다. LGMD2B 를대상으로스테로이드의이중맹검약통제연구 (double blind placebo controlled study) 가현재시행되고있다 (http://clinicaltrials.gov). 그러나, 스테로이드 2) LGMD1B (laminopathy) Lamin A/C 유전자의돌연변이로인해생긴다. Lamin A/C는 LGMD 외에도관절구축과부정맥, 근력약화를보이는상염색체우성의 Emery-Dreifuss 근육디스트로피의대표적인유전자이기도하다. 근력약화가나타날때부정맥뿐만아니라진행하는심근병증의동반는경우도흔하기때문에주의가필요하다. 3) LGMD1C (caveolinopathy) Caveolin 3 유전자이상은고CK혈증 (hyperckemia) 부터잔물결근육병 (rippling muscle disease), 원위부근육병 (distal myopathy), 근위부근육병 (proximal myopathy) 까지 Korean Journal of Neuromuscular Disorders 2012 19
Korean Journal of Neuromuscular Disorders Vol. 4, 2012 다양한임상양상을보인다. 근력약화에대한장기간동안의기록은없으나, 점진적으로진행하는것으로생각된다. 19 혈중 CK는정상의 10배이상으로증가한다. 4) LGMD2A (calpainopathy) LGMD2A는 calpain 3 유전자의결함으로생기는가장흔한아형으로전체 LGMD 의 20~40% 에해당된다. 일반적으로 8-15세에근위부근육의위약으로시작되나성인에서의증상발현도흔하고진행속도도다양하다. LGMD2A 은다른아형과비교할때호흡근육의보존되나, 날개견갑골 (winged scapula), 발목인대구축, 전만증 (lordosis) 이흔한것이특징이다. 검사실소견상혈중 CK수치는정상의 10배이상으로증가한다. 증상발현후 10-20년후에는보행능력이상실되는것으로알려져있다. 3 진단을위해서는웨스턴블럿과유전자검사가흔히사용된다. 그러나 calpain 3단백은쉽게손상되고, 분자량은정상이나기능은못하는경우도있어서웨스턴블럿을통한진단에어려움이있다. 그러나유전자검사도일반적방법으로는의심환자의 23% 정도에서는두개중한개의돌연변이만을찾을수있었다. 3 5) LGMD2B (dysferlinopathy) LGMD2B는 dysferlin 유전자의결함으로생기는두번째로흔한아형으로전체 LGMD 의 18% 에해당된다. Dysferlin 은또한가자미근 (gastrocnemius) 을침범하는 Miyoshi 근육병의원인유전자이기도하다. 근력약화는 15-35 세에나타나는, 경우가많으나표현형은고CK혈증을포함하여다양하다. 일반적으로초기에는하지의뒷쪽근육이먼저손상되고상지는보존된다. 이아형에속하는환자들의상당수가증상발현전에는다른아형들과당리운동선수로뛸정도로운동능력이좋았다는보고가있다. 20 검사실소견상혈중 CK는 10배이상으로증가된다. 근육조직검사상염증세포의침윤이흔해서단백결손을확인하지않으면, 근육조직검사후염증성근육염으로오진되는경우도종종있다. 이와같은특징은한국인환자에서도공통적으로확인할수있었다. 21 6) LGMD2C-F (sarcoglycanopathy) Sarcoglycan 복합체를이루는 α-, β-, δ-, γ-, and δ-sarcoglycan 의손상으로나타난다. Sarcoglycan 복합체는 dystrophin과함께 dystrophin 연관복합체를이루기때문에듀센형또는베커형근육디스트로피와유사하다. 22,23 다만상염색체열성으로유전하고, 날개견갑골 (winged scapula) 이흔하다는점은차이가난다. 아동기에증상을발현하여빠른 진행을하는것이일반적이나성인기에발병하여천천히진행하는경우도있다. 종아리비대 (calf hypertrophy) 가흔하고증상발병시부터상지어깨주변근육의침범이흔하다. 근력약화의진행에따라서호흡근육의장애및심근병증도나타난다. 혈청 CK는정상의 10-70배까지높이증가한다. Sarcoglycan의한아형의결손은전체복합체의결손으로이어지기때문에병리조직의면역조직화학염색에서는아형에상관없이모든 sarcoglycan의아형의결손으로관찰된다. 따라서정확한아형의손상을확인을위해서는유전자검사가요구된다. 유럽과북미지역에서는 α-sarcoglycan의소실이대부분인반면, 북아프리카지역에서는 γ-sarcoglycan의소실이많다. 2 브라질의경우에서는 LGMD2C (γ-sarcoglycan) 가 23%, LGMD2D (α -sarcoglycan) 가 40%, LGMD2E (β-sarcoglycan) 가 23%, LGMD2F (δ-sarcoglycan) 이 14% 의빈도로보고되었다. 24 일반적으로는 LGMD2D (α-sarcoglycanopathy) 가가장흔하다고알려져있다. 7) LGMD2G (telethoninopathy) 골격근과심간의 Z-disc에존재하는 telethonin의이상으로나타나는아형으로임상증상이미약하고브라질과중국인에서드물게보고되고있다. 일반적으로 9~15세에발현되지만천천히진행하여서 40대가되어서야보행이불가능해진다. 심장근육의침범은흔하고혈중 CK농도가 3~30배까지증가하는것으로알려져있다. 근육조직검사소견상테를두른공포 (rimmed vacuole) 와 telethonin의결손을확인할수있다. 8) LGMD2H TRIM32 유전자의손상으로나타나는유전병으로캐나다의후터파교인에서처음확인되었다. 20대중반에증상이발현되어서서히진행하고, 혈중CK농도는정상의 5배정도로상승한다. 9) LGMD2I and other types of LGMD caused by proteins altering α-dystroglycan LGMD2I 는 α-dystroglycan의 gylcosylation에관련된 Fukutin related protien (FKRP) 의손상으로나타나는북유럽에서흔한아형이다. 임상적으로베커형근육디스트로피와유사형늦은소아기에증상이발현하고종아리의비후, 가로막근육의침범으로인한호흡장애, 심근병증을흔히보인다. LGMD2I 에서 α-dystroglycan이손상되지는않지만 glycosylation 의장애가생겨서 α-dystroglycan단백의발현이감소 20 대한신경근육질환학회지 2012
HJ Park, et al. Diagnosis and Therapy of Limb Girdle Muscular Dystrophy 된다. 이처럼 α-dystroglycan의 glycosylation을억제시키는아형으로 POMT1 유전자이상에의한 LGMD2K, fukutin유전자이상에의한 LGMD2M, POMT2유전자이상에의한 LGMD2N, POMGnT1 유전자이상에의한 LGMD2O가있다. 따라서일반적으로면역조직화학검사상 α-dystroglycan 이발현되지않는다면가장흔한 FKRP유전자를확인한후이상이없다면다른유전자를확인한다. 10) LGMD2J(Titinopathy) LGMD2J 는 titin 유전자의동형접합돌연변이 (homozygous mutation) 를갖는핀란드의한가계에서처음보고되었다. 같은유전자의이형접합돌연변이 (heterozygous mutation) 는원위부근육병으로나타난다. 10대와 30대사이에근력약화가발현되어빠르게진행하며혈중 CK수치는 10배이상증가한다. LGMD2J 에서 calpain 3가검출이안되거나저하되는경우가많아서 titin과 calpain 3사이에연관관계가있 을것으로추정된다. 11) LGMD2L (anoctaminopathy) LGMD2L는최근에야알려지기시작하는아형으로칼슘활성염소통로로추정되는 anoctamin 5 유전자의돌연변이가원인이된다. 표현형으로근위부의근력약화를보이는 LGMD 형과 Miyoshi근육병처럼종아리근육의약화를주로보이는원위부형이있다. 20대에서 50대사이의성인에서주로증상이나타나고, 연국과독일에서는비교적흔한아형으로 founder mutation 이있는것으로보고되고있다. 25 혈중 CK농도는 10배이상으로증가한다. 6. 증례 1) Case 1 15 세경시작된하지의근력약화를주소로 22 세여자가 A B C D Figure 2. Pathologic features of Case 2. (A) Prominent inflammatory cell infiltration and increased endomysial fibrosis on H&E stain ( 200). (B) A few necrotic (*) and regenerating muscle fibers (black square) on modified Gomori trichrome stain ( 200). (C) Dysferlin in a normal muscle specimen by immunohistochemistry ( 200), (D) Loss of dysferlin by immunohistochemistry ( 200). Korean Journal of Neuromuscular Disorders 2012 21
Korean Journal of Neuromuscular Disorders Vol. 4, 2012 내원하였다. 1세경심장판막수술외의다른과거력및가족력은없었다. 근력은서서히진행하여 17세부터는계단을오르거나팔을높이드는것이힘들졌다. 내원시시행한신체검사상양측발목인대구축과 Gower 징후가있었다. 호흡장애, 구어장애, 삼킴장애는없었다. 신경학적검사상뇌신경장애는없었으나상지에서 medical research council (MRC) grade IV, 하지에서 grade III의대칭적근력약화가있었다. 근위부의근력이원위부보다약하였다. 감각이상은없었고건반사는감소되었다. 혈중 CK 농도는 1904였고, 전기생리학적검사상근육병을시사하는소견이관찰되었다. 임상양상을종합할때명확한가족력없이청소년기에시작된 8배이상혈중 CK의수치가증가된근육병이었다. 지대형근육디스트로피중비교적흔한 LGMD2A 와 2B 중에서도발목인대의구축이있어서 2A의가능성을높게보았다. 환자는근육생검을거부하였고, 2A의원인유전자인 calpain3의돌연변이검사상 c.1795dupa의동형접합돌연변이 (homozygous mutation) 를확인할수있었다. 2) Case 2 14세경부터시작된하지의근력약화를주소로 30세남자가내원하였다. 환자는과거력및가족력상특이사항이없었다. 13세까지는 100 m달리기에서항상 1-2등일정도로운동능력이탁월하였다. 14세부터달리기는반에서중간정도로느려졌으나여전히아버지의일을돕기위해서 40 kg의쌀가마니를들고다녔다고하였다. 17세경부터걸음걸이가바뀌고앉았다가일어나는것이힘들어졌고주로하지가매우느리게진행하여서 30세에본원에내원하였다. 내원당시환자는구어장애, 연하곤란, 복시, 및호흡곤란은없었다. 신체검사상견갑골, 관절구축및근육의가성비대는없었다. 신경학적검사상뇌신경기능장애는없었으나상지에서 MRC grade IV, 하지의근위부에서 grade IV-, 원위부근육중발등굽힘 (dorsiflexion) 근육은 grade IV, 발바닥굽힘 (plantar flexion) 근육은 grade IV-의위약이있었다. 감각장애및소뇌기능의장애는없었다. 혈중 CK 농도는정상의 40배이상증가되었고심전도는정상이었다. 전기생리학적검사상전신형근육병에합당한소견이관찰되었다. 하지 MRI는가쪽후방근육군 (lateral posterior muscle group) 의심한근육소실과지방대체를보여주었다. 임상양상을종합할때환자는가족력이없이청소년기에시작되어주로하지의뒷쪽구역의근력약화가심하고혈중 CK농도가 10배이상으로올라가는근육병이었다. 이를토대로 LGMD 중에서도 2B (dysferlinopathy) 를의심하고근육조직검사를시행하였다. 조직검사상많은퇴행세포 (degenerative cell) 와재생세포 (regenerative cell) 및많은염증세포들의침윤을확인할수있었다 (Fig. 2A). 면역조직화학염색상 dysferlin단백의소실을확인하여 LGMD 로진단할수있었다 (Fig. 2B). 환자는내원 3년후부인의임신문제로유전자검사를위해내원하였다. dysferlin 유전자 (Reference cdna Sequence: NM_001130987.1) 의 c.1380+2t>c 와 c.2548c>t의이형접합돌연변이 (heterozygous mutation) 를확인할수있었다. 결론 LGMD 는처음정의된후로진단되지않은유전성근육병의감별진단용진단명으로주로사용되어왔다. 20여년간의분자생물학의발달로각아형의유전자및임상양상의차이를확인할수있게되었다. 임상양상, 근육조직검사, 유전자검사순으로이루어지던현재의진단방법은차세대염기서열분석의발전으로유전자검사의비용과노력이감소하면서점차근육조직검사없이유전자검사를시행하는방향으로바뀌고있다. 그러나이것은소실된단백의확인이라는확인절차가없어져서잘못된유전자검사로환자를오진할수있는가능성이높아질수있다. 따라서임상양상에대한보다자세한분석이요구될것이고, 이에대한많은연구가필요할것이다. 또한현재는보전적인치료법뿐이지만분자치료에대한지속적인연구로가까운시일내에치료법에대한가시적인성과가나올것으로생각된다. REFERENCES 1. Walton JN, Nattrass FJ. On the classification, natural history and treatment of the myopathies. Brain 1954;77:169-231. 2. Vainzof M, Bushby K. Disorders of voluntary muscle. In: Karpati G, Hilton-Jones D, Bushby K, Griggs RC. 8th ed. New York: Cambridge Univ Pr 2010;230-256. 3. Bushby K. Diagnosis and management of the limb girdle muscular dystrophies. Pract Neurol 2009;9:314-323. 4. Guglieri M, Magri F, D'Angelo MG, Prelle A, Morandi L, Rodolico C, et al. Clinical, molecular, and protein correlations in a large sample of genetically diagnosed Italian limb girdle muscular dystrophy patients. Hum Mutat 2008;29:258-266. 5. Boyden SE, Salih MA, Duncan AR, White AJ, Estrella EA, Burgess SL, et al. Efficient identification of novel mutations in patients with limb girdle muscular dystrophy. Neurogenetics 2010;11:449-455. 6. Nguyen K, Bassez G, Bernard R, Krahn M, Labelle V, Figarella- Branger D, et al. Dysferlin mutations in LGMD2B, Miyoshi myopathy, and atypical dysferlinopathies. Hum Mutat 2005;26:165. 22 대한신경근육질환학회지 2012
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